We present abundance measurements of elements O, C, Si and Fe for three gas-rich galaxies at z∼5 using observations from the Very Large Telescope (VLT) and the Keck telescope in order to better constrain the early chemical enrichment of gas-rich galaxies. These galaxies show strong Lyman-α absorption in the spectra of background quasars, with neutral hydrogen column densities log N H I (cm −2 ) = 20.10±0.15, 20.10±0.15, and 20.80±0.15. Using the undepleted element O, we find the metallicities [O/H] to be in the range of −2.51 to −2.05 dex. Our study has doubled the existing sample of measurements of undepleted elements at z > 4.5. Combining our measurements with those from the literature, we find that the N H I -weighted mean metallicity of z∼5 absorbers is consistent with the prediction based on z < 4.5 DLAs. Thus, we find no significant evidence of a sudden drop in metallicity at z > 4.7 as reported by some prior studies. We also determine the extent of dust depletion using a combination of both the volatile element O and the refractory elements Si and/or Fe. Some of the absorbers show evidence of depletion of elements on dust grains, e.g. low [Si/O] or [Fe/O]. The relative abundances of these absorbers along with other z∼5 absorbers from the literature show some peculiarities, e.g. low [C/O] in several absorbers and high [Si/O] in one absorber. Finally, we find that the metallicity vs. velocity dispersion relation of z∼5 absorbers may be different from that of lower-redshift absorbers.

We present seven new abundance measurements of the elements O, C and Si at z > 4.5, doubling the existing sample of weakly depleted elements in gas-rich galaxies, in order to constrain the first ∼1 billion years of cosmic metal evolution. These measurements are based on quasar spectra of damped Lyman-alpha absorbers (DLAs) and sub-DLAs obtained with the Magellan Inamori Kyocera Echelle (MIKE) and Magellan Echellette (MagE) spectrographs on Magellan-South, and the X-Shooter spectrograph on the Very Large Telescope. We combine these new measurements with those drawn from the literature to estimate the N H I -weighted binned mean metallicity of −1.51 ± 0.18 at z = 4.8. This metallicity value is in excellent agreement with the prediction from lower redshift DLAs, supporting the interpretation that the metallicity evolution is smooth at z ∼ 5, rather than showing a sudden decline at z > 4.7. Furthermore, the metallicity evolution trends for the DLAs and sub-DLAs are similar within our uncertainties. We also find that the [C/O] ratios for z ∼ 5 DLAs are consistent with those of the very metal-poor DLAs. Additionally, using [C/O] and [Si/O] to constrain the nucleosynthesis models, we estimate that the probability distributions of the progenitor star masses for three relatively metal-poor DLAs are centered around 12 M to 17 M . Finally, the z ∼ 5 absorbers show a different metallicity-velocity dispersion relation than lower redshift DLAs, suggesting that they may be tracing a different population of galaxies.

We present gravitational-arc tomography of the cool-warm enriched circumgalactic medium (CGM) of an isolated galaxy (“G1”) at z ≈ 0.77. Combining VLT/MUSE adaptive-optics and Magellan/MagE echelle spectroscopy we obtain partially-resolved kinematics of Mg ii in absorption and [O ii] in emission. The unique arc configuration allows us to probe 42 spatially independent arc positions transverse to G1, plus 4 positions in front of it. The transverse positions cover G1’s minor and major axes at impact parameters of ≈10 − 30 kpc and ≈60 kpc, respectively. We observe a direct kinematic connection between the cool-warm enriched CGM (traced by Mg ii) and the interstellar medium (traced by [O ii]). This provides strong evidence for the existence of an extended disc that co-rotates with the galaxy out to tens of kiloparsecs. The Mg ii velocity dispersion (σ ≈ 30 − 100 km s−1, depending on position) is of the same order as the modeled galaxy rotational velocity (vrot ≈ 80 km s−1), providing evidence for the presence of a turbulent and pressure-supported CGM component. We regard the absorption to be modulated by a galactic-scale outflow, as it offers a natural scenario for the observed line-of-sight dispersion and asymmetric profiles observed against both the arcs and the galaxy. An extended enriched co-rotating disc together with the signatures of a galactic outflow, are telltale signs of metal recycling in the z ∼ 1 CGM.

Every lay farmer as well the commercial growers use chemical pesticides to kill pests and weeds and to get rid of diseases in their farm with aim of increasing production. Though the use of pesticides has some advantages of increase in yield, its haphazard and excessive use also create a serious impact on the environmental components and human health. The present scenario of pesticide use doesn’t seem to be satisfactory, so-called safe pesticides are also showing their ill effects in the long run and the problems such as bio-accumulation, bio-magnification are being magnified day after day. Almost all the corners of the earth and organisms living in it and those who are yet to be born have already been affected by so-called boons to pest control. This study attempts to study the present pesticides use scenario of Nepal and also the ill-effects of pesticides on human health as well as on the environment. The relevant data and information were collected from the thorough study of the journal articles, research papers, reports and various literatures. This paper pleads and sensitizes the readers to get directed toward more holistic, sustainable, natural and safe production and management practices.

Rice is the staple food crop for more than half of the world’s population though it’s cultivation is done in only 11% of the world’s cultivable land. Several pests attack rice in different ways at different stages. Increased reliance on pesticides for pest control is found to be unsustainable and cost-ineffective. So, Integrated Pest Management (IPM) has been introduced as the best alternative for pest management in rice. IPM in rice helps to minimize risks to the environment and human health. Rice IPM uses the combination of cultural, use of resistant varieties, biological, physical, and chemical practices for pest control. Farmers Field School has been the most effective way to increase IPM knowledge among rice farmers. Such training helps to facilitate the farmers to apply ecologically informed farming practices. There are several challenges regarding the implementation of rice IPM. To increase IPM implementation in rice emphasis should be given on farmers’ training and education. The role of government is also vital for the successful implementation of IPM. This review article provides an overview of various IPM practices being performed in rice fields at present.